Color & Spectra

Purpose:

            The purpose of this laboratory experiment is to explore the emission and absorption properties of white light as well as different emissions and absorptions of other sources that contain only one type of element. The spectra lines will be viewed through a diffracting gradient and then marked to perform the necessary calculations. Once this is done with white light, it will then be repeated with hydrogen to compare the two observations. After that, an unknown gas will be viewed and identified using an absorption chart found online to determine the identity of the unknown.

Procedure:

            The first step that was done this experiment was the light source was obtained and placed in front of the defrating gradient. The distance of this gap was recorded.

The light source was then turned on and the spectra was viewed through the gradient. Once the spectra was found, the middle of each primary color was marked and the distance from that point to the light source was measured and recorded.

Once this was completed, all the tabulated data was stored to be used to calculate the wavelength at a later time. Once all the necessary recordable data for the white light was obtained, the hydrogen atom emitting light was then placed in front of the gradient to have the process repeated.

Again, as done previously with the white light, the spectra of the hydrogen light was observed and the observable spectrum lines were located and measured from the light source.

The same procedure was followed as before for the white light. Next, the unknown gas light was received and placed using the exact same set up as for the previously two light sources.

Again, the spectra was viewed and measured to make the necessary calculations later on in the experiment.

Data Analysis:

            The following table represents the observed data as well as the calculated and known wavelength of the different colors in white light. In the chart, l represents the distance from the light source to the gradient, x is the distance from the light source to the spectra line, d is the spacing between the gradient, and the last two coulombs represent the experimentally calculated wavelength and theoretical wavelength respectfully.    

Color	l (cm)	x (cm)	d (cm)	Exp λ (nm)	Act λ (nm)
Red	190 ± 1	73.0 ±1	.0002	717 ±17	750
Yellow	190 ± 1	53.5 ±1	.0002	542 ±23	570
Green	190 ± 1	48.5 ±1	.0002	495 ±23	510
Blue	190 ± 1	45.0 ±1	.0002	461 ±23	475
Violet	190 ± 1	37.0 ±1	.0002	382 ±22	390

The proceeding table contains the information gathered from the hydrogen spectrum. Again as before, the same variables from the previous table, represent the same values as before. 

Color	l (cm)	x (cm)	d (cm)	Exp λ (nm)	Act λ (nm)
Red	190  ± 1	67.0 ±1	.0002	675 ±23	656
Blue	190  ± 1	48.3 ±1	.0002	490 ±23	486
violet	190  ± 1	43.0 ±1	.0002	441 ±22	434

The last table below is the table that contains all the data recorded for the unknown gas that was given and analyzed. Again as before, the same variables in the table represent the same measurements as the formal tables. However since this is an unknown gas, the actual wavelength section of the table is not included. 

Color	l (cm)	x (cm)	d (cm)	Exp λ (nm)
Red	190 ±1	59.5 ±1	.0002	597 ±23
Orange	190 ±1	58.5 ±1	.0002	588 ±20
Yellow	190 ±1	56.0 ±1	.0002	565 ±21
Blue	190 ±1	49.0 ±1	.0002	499 ±23

After all of these calculations were made, the spectrum of a number of gasses was displayed and the gas that closely matched the above data was chosen to be determined as our unknown. In this case, our unknown gas was accurately guessed to be mercury. The actual wavelength of the emitted lights is listed below. 

Color	Act λ (nm)
Red	623.4
Orange	615.2
Yellow	577.0
Blue	502.5

Using the data now known, we were able to determine the measurements of the uncertainty of our measurements which follows:

Conclusion:

           From this experiment, we were able to determine the identity of an unknown gas by simply using the viewable spectra of the gas. This is because every element has its own unique emission spectra as well as absorption spectra. As long as the elements spectrum is known, the identity of an unidentified element can be accurately determined by using its spectra and comparing it to that of other elements. This procedure can be repeated and executed to a relatively accurate degree of uncertainty.